The present invention relates to depth adjusting systems for tools and, in particular, to an adjustable depth locator for power-driven screwdrivers.
Power-driven screwdrivers frequently are equipped with depth locators that are releasably mounted to the nose of the tool and surround the screwdriver bit for adjustably setting the depth to which the head of the screw will be set into the workpiece. In particular, the axial position of the depth locator is typically adjustable relative to the tool bit so as to control the extent to which the screwdriver bit protrudes from the end of the depth locator. Consequently, as the screw is driven into a workpiece, the end of the depth locator will contact the surface of the workpiece thereby unloading the axial pressure on the screwdriver bit which serves to disengage the clutch mechanism in the power-driven screwdriver.
It is desirable for depth adjusting systems to be easily adjusted and also readily removable from the tool housing while maintaining the depth setting to enable the operator to conveniently replace the screwdriver bit. A known depth adjusting system is shown in U.S. Pat. No. 4,647,260 to O'Hara et al., and assigned to the assignee of record of the present invention. The depth adjusting system disclosed in this patent comprises a two-piece molded plastic subassembly that is connected to the forward end of the housing of the power tool. The subassembly comprises an adjustment collar that is mounted to the nose portion coaxial with the tool bit so as to be restrained from axial movement but free to rotate relative to the housing, and a depth locator that is threadably connected to the adjustment collar and restrained from rotating relative to the housing but free to move axially relative to the housing in response to rotation of the adjustment collar. The adjustment collar is provided with an internal annular flange that is engageable via a snap-action with a retaining ring located on the nose portion of the housing. In addition, indexing means in the form of a plurality of circumferential resilient fingers are provided on the adjustment member for engaging detents on the nose portion of the tool and serve to settably maintain the adjustment member in a predetermined angular position relative to the housing. The resulting depth adjusting system disclosed in this patent enables an operator to disconnect the subassembly by unsnapping the adjustment member from the housing without disturbing the previously set depth adjustment.
It is further desirable, however, to provide a depth adjusting system that is more convenient to remove from the nose portion of the housing and that provides a greater mechanical advantage in rotatably adjusting the position of the adjustment member.
The present invention comprises an improvement over the depth adjusting system disclosed in the aforementioned patent providing an improved interface between the adjusting member and the forward end of the housing. In particular, the adjustment member in the present invention is provided with an enlarged cylindrically shaped collar portion having a pair of axially extending, cantilevered spring fingers with hook portions formed on their free ends for releasably engaging an internal circular groove in the housing opening. The cantilevered spring fingers are integrally formed at radially opposed locations on the collar portion of the adjustment member so that the adjustment member can be readily removed from the housing by simultaneously squeezing both spring fingers to disengage the hook portions of the fingers from the groove in the housing. In normal operation, however, the engagement of the hook portions of the resilient fingers in the internal groove in the housing enables the adjustment member to be freely rotated relative to the housing. Preferably, indexing means similar to that described in the aforementioned patent are also provided to maintain the adjustment member in a set angular position relative to the housing. Raised ribs integrally formed on the outer surface of the enlarged collar portion of the adjustment member, together with the greater size of the enlarged collar portion, also enable the operator to more easily adjust the angular position of the adjustment member.